Ion kinetic energy measurements in two soft ion ejection methods from a quadrupole ion trap

The kinetic energy of ion beams upon ejection from a quadrupole ion trap was measured in view of coupling quadrupole ion traps with other mass analyzers. Measurements were performed using a retarding grid analyser for two modes of ion ejection from the quadrupole ion trap based on the decrease of the amplitude of the radiofrequency voltage on the ring electrode simultaneously combined with the application of: (i) a positive voltage on the ring electrode and (ii) a voltage between the end-cap electrodes. We show that ion kinetic energy at ejection depends on the DC ejection voltage and the amplitude of the RF voltage at the moment of ejection, which means that the kinetic energy of the ions that are ejected from the ion trap depends on the m/z ratio. Ion focusing depends on the depth of the pseudo-potential well in the quadrupole ion trap.

Graphical abstractThe ion kinetic energy is measured after ejection from a quadrupolar ion trap at low radiofrequency voltage with a DC voltage to optimize couplings with other analyzers.Figure optionsDownload full-size imageDownload high-quality image (8 K)Download as PowerPoint slideResearch highlights▶ Ions are ejected at higher RF voltages than expected along the βz = 0 line. ▶ Ion ejection efficiency increases with DC voltages on the ion trap. ▶ Ion kinetic energy increases with DC voltage at ejection. ▶ Ion kinetic energy increases with RF voltage amplitude at ejection.